The invention relates to an apparatus for laterally aligning one fabric edge or two fabric edges during sewing, and more particularly to apparatus for detecting the lateral position of the fabric edge transversely of the sewing direction and generating a sensor signal, and which includes a guide mechanism controlled by the sensor signal for laterally aligning the fabric edge during sewing.
Especially with industrial automatic sewing machines, in particular machines for contour sewing, it is important to have available an auxiliary means at high working speeds which takes care in partly or completely automatic manner that the fabric edge assumes the prescribed lateral position in quite exact fashion. It is conceivable to keep the fabric on a prescribed path by means of stopper devices. However, this is an insufficient auxiliary means because, especially in case of different curves, the fabric may fold at the lateral stop and thus no longer takes the desired position during conveyance thereof.
It is also conceivable to pass the fabric between a pressing plate and a wheel in order to adjust the wheel in response to a fabric edge sensor signal in such a manner that the fabric edge takes the desired position. However, such a way of guiding presents a problem in that the fabric must be fed to the sewing head with as little tension as possible and that the application of a wheel would distort the fabric. German patent DD-132 508 (corresponding to published application DE 28 22 634 Al) shows such a possibility in which the fabric slides axially past the circumference of the wheel. For reducing this friction, French FR-2 585 378 shows a wheel having rolling discs distributed across the circumference thereof. However, here too only a particular point of the wheel abuts the fabric so that undesired distortions may result in the fabric.
Therefore, it is an object of the invention to provide an apparatus for laterally aligning a fabric edge during sewing, that permits exact alignment of the edge while presenting virtually no resistance to the fabric conveying motion effected by the sewing machine, and that leaves the fabric virtually without any tension.